The present invention relates to a melt spinning method and an apparatus used in the method for manufacturing a nonwoven fabric by supplying, onto a conveyor belt, fibers formed by extruding melted resin by using a melt blowing method.
The melt blowing method is a melt spinning method for obtaining a nonwoven fabric sheet from fibers (threads) obtained by melting and extruding raw resin. By the melt blowing method, melted raw resin is cast into a mold and extruded by an extruder from a nozzle provided on the mold and, simultaneously, supplied with hot and high velocity airflow from the periphery of the nozzle so that the melted resin may be blown into a shape of fibers (threads). The fibers are supplied onto a conveyor and laminated, to manufacture a nonwoven fabric sheet.
As for this type of spinning method, for example, a laterally arranged web manufacturing method is known which is disclosed in Japanese Laid-Open Patent Publication No. 2001-98455. That is, the method includes a step of extruding melted resin from a spinning nozzle into the shape of fibers; a step of blowing hot primary air from the periphery of the spinning nozzle to vibrate the fibrous melted resin; a step of blowing hot secondary air toward the fibrous melted resin as it vibrates and falls due to the primary air, so that the resin may be spread in a widthwise direction and spun; and a step of laminating the fibrous melted resin onto a conveyor to manufacture laterally arranged webs.
However, the manufacturing method described in the above publication aims at obtaining webs arranged laterally, so that it is necessary to vibrate fibrous melted resin extruded from a spinning nozzle by using primary air and spread it in a widthwise direction by using secondary air. In this case, since the fibrous melted resin extruded from the spinning nozzle is vibrated by blowing the primary air at a high velocity, the fibers may not be elongated stably and, moreover, may be cut easily. In addition, since the secondary air is blown to the fibrous melted resin laterally, the fibers may flow in a turbulent manner and be cut easily, leading to a problem that the fibers cannot easily be formed to be thin and uniform.